[Bldg-sim] modeling chilled beams in eQuest

Thu May 6 08:42:49 PDT 2010

The other thing at work here is that the Induction units and the DOAS are
constant volume, so you're going to pay a fan energy penalty for this - so
first, make sure you only have one zone per Induction unit in eQUEST.  In
real life, the DOAS can send variables amounts of air (based on load) to
chilled beams, but this can't be modeled with the Dummy zone/DOAS approach.
If you change the system type to a Power Induction Unit (which is a VAV) and
you zero out the fan power, this might work.

There is no induction ratio parameter then, but I have played around with
that parameter in eQUEST and seen almost no impact from varying it.

I am attempting to modeling an active chilled beam system served by a VAV
DOAS right now, so if anyone else has comments on the Power Induction Unit
approach, please let me know!

Kendra Tupper, PE, LEED AP
Senior Consultant
Built Environment Team

Rocky Mountain Institute  |  T  303-567-8641 |  F  303-245-7213  |
www.rmi.org

On Thu, May 6, 2010 at 9:37 AM, Ellen Franconi <efranconi at rmi.org> wrote:

> Vishnu,
> I am not sure I completely follow what you did but perhaps you are not
> aware that the induction unit system includes a central fan for pretreating
> outside air delivered to the induction units. So if you used the "outside
> air from sys" approach,the central fan of the induction unit would still be
> modeled with its default parameters. Also, if you don't set the induction
> ratio high enough (e.g. default is 3, max value is 10), you will get return
> air mixing with your supply (e.g it will no longer be 100% OA), which will
> make your supply air flow higher. This will increase your fan energy use as
> well.
>
> I don't think the eQUEST documentation includes a description of the
> induction unit system (TPIU or FPIU) but its relevant keywords can found in
> the DOE2.1E BDL Summary. You could also insert the following commands in
> your input file.
>
> DIAGNOSTICS  DEFAULTS ..   $ before the SYSTEM command and
> DIAGNOSTICS  CAUTIONS ..    $ after the SYSTEM command
>
> Adding the above will show in the BDL file the value for all keywords not
> explicitly listed but with default values being used.
> Ellen
>
>  On Wed, May 5, 2010 at 11:14 PM, Vishnuraj Nair <vishnu at kalpakrit.com>wrote:
>
>>  Dear friends,
>>
>>
>>
>> I am modeling the active chilled beams system using an induction unit. I
>> have created a separate treated outside air system (TOAS) from where the
>> fresh air would be supplied to
>>
>> the induction unit. I have hard coded the fresh air requirement for each
>> zone at the outdoor air CFM field under outside air tab as well as under
>> design flow cfm field under air flow tab
>>
>> so that the only the fresh air requirement is supplied to the zone. The
>> cooling will be done by chilled beams modeled as induction unit.
>>
>>
>>
>> when I see the simulation report the amount of fan energy consumed is huge
>> which is nearly about 20% percent of the overall energy consumption.
>>
>> So then I zeroed out the fan energy i.e kW/CFM for fans =0 and only the
>> TOAS has the fan energy but the fan energy consumption decreased very
>> little.
>>
>> I have no other source in the model for which the fan energy could be
>> accountable for.
>>
>>
>>
>> Can anyone please tell what can be the reason for this or if I am missing
>> out on something?
>>
>> Am I modeling the system right? How is the fan energy for this system to
>> be modeled?
>>
>> Vishnuraj Nair
>>
>> Kalpakrit Sustainable Environments Pvt. Ltd.
>>
>> New Delhi
>>
>> Tel: +91.124.4309490-92 Ext: 312 , Fax: +91.124.4309493
>>
>> E-mail : vishnu at kalpakrit.com
>>
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>
> --
> Ellen Franconi, PhD, LEED AP
> Senior Consultant, Built Environment Team
>
> Rocky Mountain Institute
> 1820 Folsom Street
> Boulder, CO 80302
> 303.567.8609 (Desk)
> 303.245.7213 (Fax)
>
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